B_{λ}(T) = \frac{2hc^{2}/λ^{5}}{e^{hc/λkT} − 1}

Integrated energy per second over a wavelength range

W/m^{2} = (π) ∫_{λ_{2}}^{λ_{1}} \frac{2hc^{2}/λ^{5}}{e^{hc/λkT} − 1}dλ